Since the season of goodwill and general cheerfulness is approaching, it seems wrong to present even more bad news for this rather dismal year, yet we cannot hide from it, The problem was presented in Nature ( https://doi.org/10.1038/d41586-021-03758-y and relates to the Thwaites glacier. This glacier flows off the Antarctic continent into the Southern ocean. The glacier is 120 kilometers wide and about two thirds of this flows into the Southern Ocean, but one third runs into its eastern ice shelf. Here, the flow grinds to a halt because the ice out at sea hits an underwater mountain that is about 40 kilometres offshore. The Mountain is stopping the ice from flowing.
Unfortunately, thanks to the warmer water flowing underneath, that part of the glacier is becoming unstuck from the mountain, and this is causing cracking and fracturing across parts of the ice shelf. The fractures are propagating through the ice at several kilometres per year, and are heading towards thinner ice, which may lead to the whole lot shattering. To add to the problem there is tidal flexing as the glacier starts to separate from the rock and the “up and down” movement with the tides causes the glacier to flex further upstream, including where it is over land. Because of this flexing, warm water from the Southern Ocean could make its way beneath the glacier more easily.
Current estimates are that this mass of ice over the water could shatter within five years, which would release an huge mass of icebergs into the Southern Ocean, and the whole glacier could start flowing much faster into the sea. That means sea level rise. Currently the Thwaites already loses around fifty billion tonnes of ice each year and causes 4% of global sea level rise. If this eastern ice shelf collapses, ice would flow three times faster into the sea. If the glacier were to collapse completely sea levels would rise 65 centimetres. The glacier itself is moving towards the sea at about a mile each year. This is a fairly fast moving glacier.
So, what do we do about it. In this case it is probably impossible to do much. There is no way to stop a glacier moving. The only possible thing to do to stop the sea level rise would be to somehow engineer more snow to fall further inland to Antarctica. Fifty billion tonnes of snow each year would cancel out the sea level rise, but we all know that is not about to happen any time soon. But not to worry. Senator Manchin does not believe in climate change as a hazard, and he will torpedo President Biden’s efforts to get the US to do something. This Senator wants to burn more coal, and this one man will torpedo everyone else’s limited efforts. So is the Senator right? No. We might not be able to stop the Thwaites, but there are worse problems downstream we can still stop if we act before they become activated. Of course, he is not alone. Australia is selling more coal, China is building more coal-foired power stations, Germany has turned of nuclear to burn lignite. A cartoon in our paper had it: the Devil was reading about our activities and he said, “Aw, no fun. They’re not even pretending to try now.”
The nature of the problem is what we call hysteresis. If you have an equilibrium, such as when there is no change of temperature in an object over time, this arises because the heat loss equals the heat input. Now, suppose you increase the heat input a little. Now we are out of equilibrium, but since the heat loss depends on the temperature what you expect is the temperature will rise to reach the equilibrium position corresponding to where the heat loss now equals the heat input. Unfortunately, it doesn’t quite work like that. Suppose I have a lump of iron, and I increase the amount of heat going into it. The surface may well get warmer, but heat then starts flowing into the inside of the object. It takes time before the object reaches the new temperature. With something like ice, it is worse. The ice will warm, but once it gets to its melting point the increased heat flowing in starts to melt the ice. The ice stays at the same temperature. If we increase the heat flow inwards there is no change, other than the ice melts faster. Then, when it has all melted, suddenly the temperature starts to increase quickly.
To some extent, that is what has happened on our planet. Our greenhouse effect has been slowing the heat loss to space, and since the heat input remains the same, effectively the system is absorbing more heat. However, to start with all that happened was the surface of the oceans warmed up and some ice melted. So we ignored the problem because we observed no change in temperature, and poured more heat in. All that did was warm more water and melt more ice. The problem then is that we have now reached the point where the increase in heat that we are pouring into the Earth is starting to reach the point where the effects that absorbed heat without altering our temperature too much have now reached the end of their capacity. We are now going to make major changes to the planet, and we cannot stop them because the forces are already in place to generate far more heat.
Another characteristic of hysteresis is you cannot reverse what you have done simply by stopping increasing the heat input. Because the ice is melting because the water is above its freezing point, if we stopped adding heat now and stopped all greenhouse emissions, the oceans are still warm and the melting continues. However, there are thresholds. One calculation (Nature 585 (2020) p 538) indicated that for every degree of global temperature rise up to 2 degrees above pre-industrial levels will lead to 1.3 metres of sea-level rise. Between 2 – 6 degrees of warming it doubles to 2.4 metres per degree, and between 6 – 9 degrees, we get an extra 10 meters per degree. Further, the nature of hysteresis is that this is irreversible. If we want to turn it around we have to reduce global temperatures to one degree below what they were in 1850.
With that dismal thought, I wish you all a very Merry Christmas and all the best for 2022. This will be my last post for the year, and as usual I shall resume in mid-January. Finally, there are still my ebooks on the Smashwords sale.